Remove DeleteTask and convert remaining users.

content/browser/download/download_manager_impl.h

Index: content/browser/download/download_manager_impl.h
diff --git a/content/browser/download/download_manager_impl.h b/content/browser/download/download_manager_impl.h
index 6966fa334f126eaa9cf4283e6f4faa2ae2495120..1fbffb371603f86e5fcc36d4d34bd18d74ac4c8f 100644
--- a/content/browser/download/download_manager_impl.h
+++ b/content/browser/download/download_manager_impl.h
@@ -16,6 +16,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/message_loop_helpers.h"
 #include "base/observer_list.h"
 #include "base/synchronization/lock.h"
 #include "content/browser/download/download_item_impl.h"
@@ -138,7 +139,7 @@ class CONTENT_EXPORT DownloadManagerImpl
       DownloadManagerImpl, content::BrowserThread::DeleteOnUIThread>;
   friend struct content::BrowserThread::DeleteOnThread<
       content::BrowserThread::UI>;
-  friend class DeleteTask<DownloadManagerImpl>;
+  friend class base::DeleteHelper<DownloadManagerImpl>;
 
   virtual ~DownloadManagerImpl();